GIFT   OF 


UNIVERSITY  OF  CALIFORNIA 
DEPARTMENT  OF  CIVIL  ENGINEERING 

TESTING   LABORATORY 


LABORATORY   INSTRUCTIONS   FOR 

TESTS  OF  CEMENT,  MORTAR 

AND   CONCRETE 


BY 

CHARLES  DERLETH,  JR. 
Director  of  the  Testing  Laboratory 

AND 

ARTHUR  C.  ALVAREZ 
instructor  in  charge 


BERKELEY,  CALIFORNIA 
January,  1912 


PREFACE 

This  manual  has  been  prepared  for  Civil  Engineering  students 
who  take  the  course  in  cement  testing  at  the  University  of  Cali- 
fornia. Its  purpose  is  to  relieve  the  instructor  from  the  detailed 
direction  of  students  and  so  afford  more  time  for  emphasizing  the 
theory  and  principles  involved. 

The  chief  objects  of  the  course  are  to  acquaint  the  student 
with  the  methods  of  testing  cement  and  cement  products,  and  to 
cultivate  habits  of  accurate  observation  and  clear  description  of 
phenomena.  It  must  be  remembered,  however,  that  skill  for  the 
production  of  uniformly  satisfactory  results  in  testing  can  be 
acquired  only  after  considerable  practice. 


TABLE   OF   CONTENTS 

PAGE 

General  Eules  for  Laboratory  Work  , 4 

Operation  of  Testing  Machines  5 

Writing  of  Eeports  6 

Fineness  of  Portland  Cement  7 

Specific  Gravity  of  Portland  Cement  9 

Determination  of  Voids  in  Concrete  Aggregates  11 

Tensile  Strength  of  Neat  Cement  and  Standard  Cement  Mortar  14 

Moulding  Cubes  for  Compression  Test  of  Cement  Mortars  17 

Moulding  Specimens  for  Compression  Test  of  Concrete  19 

Moulding  Specimens  for  Tension  Test  of  Concrete  21 

Moulding  Specimens  for  Test  of  Bond  between  Steel  and  Concrete 23 

Moulding  Reinforced  Concrete  Beams  for  Flexure  Test  of  Concrete 24 

Compression  Test  of  Cement  Mortar  Cubes  25 

Compression  Test  of  Concrete  27 

Tension  Test  of  Concrete  28 

Test  of  Bond  between  Concrete  and  Steel  29 

Reinforced  Concrete  Beam  Test  ..                                                                     ..  30 


[3] 

402939 


GENERAL  RULES  FOR  LABORATORY  WORK 

Prompt  and  regular  attendance  is  required  of  every  student. 
The  assignment  to  tests  is  posted  on  the  bulletin  board. 

Before  coming  to  the  laboratory  read  the  directions  for  the 
assigned  test  carefully;  be  prepared  to  perform  the  operations 
promptly.  Follow  the  directions  closely. 

When  the  required  specimens  or  tests  have  been  made, 
thoroughly  clean,  washing  if  necessary,  all  apparatus  used. 
Remove  all  waste  from  the  tables,  floor  or  testing  machines. 
Dry  and  oil  all  polished  surfaces  of  metal  to  prevent  rust. 

Should  any  apparatus  be  broken,  it  should  be  reported 
immediately.  Breakages  due  to  carelessness  will  be  charged  to 
the  student  responsible  for  the  damage. 

In  performing  tests,  students  working  together  should  share 
alike;  but  reports  are  to  be  written  independently. 

Keep,  for  your  own  reference,  all  original  data  of  tests  in 
neat  tabular  form  in  a  special  laboratory  log  book.  This  book 
will  be  inspected  from  time  to  time  and  called  for  at  the  end  of 
the  term. 


[4] 


OPERATION  OF  TESTING  MACHINES 

Study  the  operation  of  the  testing  machines  at  every  oppor- 
tunity until  you  are  thoroughly  familiar  with  their  principle 
and  mechanism.  The  machines  in  the  laboratory  are  in  opera- 
tion daily  and  students  are  welcome  to  witness  the  tests  at  any 
time. 

Do  not  operate  a  machine  for  the  first  time  without  the 
assistance  of  the  instructor. 

Do  not  start  a  machine  without  determining  the  direction 
and  speed  with  which  it  will  move. 

Do  not  start  a  machine  too  suddenly  as  there  is  danger  of 
stripping  a  gear  or  throwing  a  belt. 

Do  not  change  the  direction  or  speed  of  motion  without  first 
stopping  the  machine. 

Always  accurately  center  a  specimen  in  a  testing  machine 
as  the  weighing  apparatus  records  correctly  for  this  position 
only. 

Always  use  a  spherical  seated  base-plate  for  compression 
tests  so  that  the  bearing  surface  of  the  specimen  may  be  made 
parallel  to  the  upper  compression  plate  of  the  machine. 

Before  applying  the  load  in  any  test,  balance  the  weighing 
apparatus  with  the  poise  at  zero  and  the  test  piece  in  the 
machine.  Adjust  the  recoil  nuts  to  be  just  loose. 

The  speed  of  applying  the  load  should  be  such  that  the  poise 
arm  may  be  kept  balanced.  Readings  upon  a  test  piece  for  a 
certain  load  should  be  taken  only  when  the  poise  arm  is  bal- 
anced at  that  load. 

Before  leaving  a  machine  or  when  a  test  is  finished  be  sure 
that  the  clutches  are  properly  thrown  out  and  that  the  machine 
has  stopped  running. 

CAUTION. — At  times  machines  have  been  left  running  by 
operators  with  the  result  that  usually  some  part  of  the  machine 
was  broken.  You  will  be  charged  for  repairs  necessitated  by 
careless  handling  of  machines. 

[5] 


WRITING    OF    REPORTS 

Follow  strictly  the  "General  Rules  for  Notes,  Problems, 
Eeports  and  Theses"  adopted  by  the  Department  of  Civil 
Engineering  and  printed  in  the  standard  manila  folder. 

Clearness,  order  of  presentation,  legibility  of  writing  and 
neatness  will  receive  due  consideration  in  grading  the  report. 
Lack  of  neatness  is  sufficient  cause  for  rejecting  a  report. 

Observe  the  following  order  in  arranging  the  report : 

Title.    This  should  indicate  at  a  glance  the  scope  of  the  test. 

Purpose.    Give  briefly  the  object  and  significance  of  the  test. 

Material.  Describe  the  materials  tested.  Give  scale  sketches 
or  photographs  of  the  specimens  before  and  after  failure. 

Apparatus.  Name  all  apparatus.  Describe  all  special  appar- 
atus and  testing  machines  used  for  the  first  time.  Supplement 
descriptions  with  scale  sketches. 

Method  of  Test.  Describe  all  operations  which  have  any 
bearing  on  the  performance  or  success  of  the  test. 

Data.  Submit  a  tabular  transcript  of  the  essential  data  from 
the  laboratory  log  book.  Describe  the  behavior  of  the  material 
when  tested;  state  observations  of  unusual  phenomena. 

Computations.  Derive  all  formulas  involved.  Indicate  the 
numerical  work.  Ordinarily  the  computations  may  be  made 
with  a  slide  rule.  Give  a  tabular  summary  of  the  final  results. 

Conclusions.  State  the  conclusions  to  be  drawn  from  the 
results.  Compare  the  results  with  those  in  standard  text-books 
and  specifications;  discuss  the  reasons  for  any  discrepancies. 

Each  report  must  be  submitted  in  a  standard  manila  folder 
within  one  week  of  date  of  performance  of  test.  Reports  re- 
turned for  correction  are  due  one  week  from  date  of  return. 


[6] 


TEST    No.  1 

FINENESS   OF   PORTLAND   CEMENT 

Apparatus.  Chemical  balance,  one  set  of  weights,  two  sets 
of  sieves — no.  30,  no.  100  and  no.  200  with  pan  and  cover,  trowel, 
spatula,  two  pans,  brush  for  cleaning  sieves,  some  steel  shot  to 
facilitate  sieving,  four  small  sheets  of  paper  for  weighing  cement. 

Operations.  Place  about  200  grams  of  the  cement  sample 
assigned  in  a  pan  and  dry  in  the  oven  at  212°  F.  for  at  least 
thirty  minutes.  Break  any  caked  lumps  with  the  trowel.  Screen 
the  dried  sample  through  the  no.  30  sieve  and  discard  any 
residue.  Weigh  out  carefully  50.00  grams  of  the  screened 
sample ;  place  it  with  some  shot  on  the  no.  200  sieve  with  the  pan 
attached. 

Cover  the  sieve  and  shake  at  a  convenient  rate  according  to 
the  directions  in  paragraph  25,  "Standard  Methods  of  Testing 
Cement. ' '  If  the  cement  clogs  the  meshes  of  the  sieve  it  has  not 
been  sufficiently  dried.  The  sieve  must  always  be  kept  perfectly 
dry. 

The  shot  is  separated  from  the  residue  by  shaking  on  a  no.  30 
sieve. 

Eecord  the  following  weights:  1.  Weight  of  cement  passing 
no.  200  sieve.  2.  Weight  of  residue  rejected  by  no.  200  sieve. 
3.  Weight  of  residue  passing  no.  100  sieve.  4.  Weight  of  residue 
rejected  by  no.  100  sieve.  Check  the  weights  by  1  -f-  2  =  50 
grams  and  1  +  3  +  4  =  50  grams. 

Eepeat  the  determination  using  100.00  grams  of  cement. 
Each  student  will  thus  make  two  independent  tests  of  the  fine- 
ness of  the  sample  assigned. 

Students  are  cautioned  to  handle  the  no.  100  and  especially 
the  no.  200  sieves  with  extreme  care  to  prevent  injury  to  the 
mesh.  In  making  weight  determinations  brush  both  the  sieve 
and  the  pan  free  of  all  cement  dust.  In  cleaning,  use  only  the 
small  brush  provided,  and  that  very  lightly. 

[7] 


Submit  results  in  tabular  form,  giving  the  amounts  of  cement 
by  weight  and  by  percentage  which  pass  and  are  rejected  by  the 
sieves. 

What  is  the  significance  of  fineness  of  grinding  of  a  cement? 
What  are  the  standard  requirements  concerning  the  fineness  of 
Portland  cement? 

References.  Fineness  of  Cement.  1.  Practical  Cement  Testing,  by 
W.  P.  Taylor,  pages  63-80.  2.  Cements,  Limes  and  Plasters,  by  E.  C. 
Eckel.  3.  Portland  Cement,  by  E.  K.  Meade,  pages  291-298.  4.  Con- 
crete— Plain  and  Eeinforced,  by  Taylor  and  Thompson,  pages  82-87. 
5.  The  Materials  of  Construction,  by  Johnson,  pages  409-413.  6.  Pro- 
ceedings of  the  American  Society  for  Testing  Materials. 


[8] 


TEST    No.   2 

SPECIFIC   GRAVITY   OF   PORTLAND   CEMENT 

Apparatus.  Chemical  balance,  one  set  of  weights,  two  Le 
Chateliers  specific  gravity  flasks,  two  battery  jars,  two  small 
funnels,  two  glass  tubes  for  pipettes,  two  short  pieces  of  brass 
wire,  two  stands  and  clamps,  two  spatulae,  one  large  funnel  with 
filter  paper,  two  small  brushes,  two  pans,  vessel  for  waste  kerosene 
and  cement,  supply  of  kerosene. 

Operations.  Place  about  200  grams  of  the  cement  sample 
assigned  in  a  pan,  breaking  any  caked  lumps  with  a  trowel,  and 
dry  in  the  oven  at  212°  F.  for  at  least  thirty  minutes.  Allow 
the  dried  sample  to  cool. 

Determine  the  specific  gravity  in  both  ways  mentioned  in 
paragraphs  8-16, ' '  Standard  Methods  of  Testing  Cement. ' '  Each 
student  will  make  two  independent  determinations,  thus  obtain- 
ing four  values  for  the  specific  gravity  of  the  sample. 

To  insure  accurate  results  the  following  details  should  be 
observed :  After  kerosene  has  drained  from  the  sides  of  the  upper 
stem,  adjust  exact  height  at  E  by  adding  or  drawing  out  the 
liquid  with  a  pipette.  When  this  has  been  accomplished  do  not 
run  any  wire  or  glass  tube  into  the  liquid  again,  since  doing  so 
lowers  its  level.  Use  large  funnel  only  for  filling  flask  with 
kerosene.  Facilitate  the  passage  of  the  cement  through  the  small 
funnel  by  warming  it  in  the  oven  when  drying  the  cement ;  then 
polish  its  inside  surfaces,  especially  the  stem,  with  a  piece  of 
clean  cotton  waste.  Avoid  any  tendency  of  the  cement  to 
accumulate  at  the  lower  portion  of  the  bulb  C  by  shaking  the 
flask  gently. 

CAUTIONS.  Handle  the  apparatus  with  great  care.  Do  not 
allow  any  water  to  get  into  the  flask.  To  wash  the  cement  out 
and  clean  the  flask  use  kerosene  only.  Provide  a  1-inch  sand 
cushion  in  the  bottom  of  the  battery  jar.  Do  not  raise  and  drop 
the  funnel  against  the  top  of  the  flask,  but  use  a  short  wire  when 
cement  clogs  in  the  funnel. 

m 


References.  Specific  Gravity  of  Cement.  1.  Practical  Cement  Testing, 
by  W.  P.  Taylor,  pages  46-63.  2.  Portland  Cement,  by  E.  K.  Meade, 
pages  278-291.  3.  Concrete — Plain  and  Keinforced,  by  Taylor  and 
Thompson,  page  81.  4.  A  Treatise  on  Masonry  Construction,  by  Baker, 
pages  60-61.  5.  Proceedings  of  the  American  Society  for  Testing  Materials. 


[10] 


TEST    No.   3 

DETERMINATION  OF  VOIDS  IN  CONCRETE 
AGGREGATES 

Apparatus.  One  1000  c.c.  or  500  c.c.  graduate,  one  balance 
with  scoop  and  counterweight,  one  set  of  metric  weights,  one 
wooden  measuring  box,  one  water  pail,  one  galvanized  iron  meas- 
uring cylinder  with  bottom  inlet  and  tube,  scale  graduated  to 
tenths  of  an  inch,  scales  sensitive  to  one-quarter  of  an  ounce. 

Operations.  The  party  will  determine  the  voids  in  the  sand, 
gravel  and  broken  stone  samples  separately  by  each  of  the  methods 
mentioned.  Method  1  will  give  approximate  results  only  where 
the  particles  are  less  than  one-quarter  inch  in  size,  since  all  the  air 
is  not  expelled  by  the  entering  water.  It  is,  however,  well  adapted 
for  rough  determinations  in  the  field,  where  special  apparatus  is 
not  always  at  hand. 

In  both  method  1  and  method  2,  immerse  any  aggregate  which 
is  absorbent,  for  thirty  minutes,  then  remove  and  allow  the  water 
to  drain  well  from  the  surfaces  before  making  the  void  determina- 
tion. 

Method  1.  Determine  the  volume  of  the  water  pail  by  weigh- 
ing it  first  empty,  then  filled  to  the  very  rim  with  water,  and 
dividing  the  difference  in  weight  in  pounds  by  62.4. 

Fill  the  pail  with  material  and  after  shaking  to  cause  settle- 
ment, scrape  the  top  off  evenly  with  a  straight  edge.  Weigh  the 
amount  of  water  which  can  be  added  to  exactly  fill  the  pail  and 
calculate  its  volume. 

The  per  cent  of  voids  equals  the  ratio  of  the  volume  of  water 
added  to  the  volume  of  the  pail,  times  100. 

Method  2.  Determine  the  volume  of  the  cylinder  by  measur- 
ing its  average  diameter  and  height  to  the  nearest  tenth  of  an 
inch. 

Place  the  funnel  attached  to  the  rubber  tube  which  leads  to 

[11] 


the  bottom  of  the  measuring  cylinder  in  the  lower  rack  which  is 
level  with  the  bottom  of  the  cylinder.  Fill  the  tube  and  funnel 
with  water  to  the  bottom  level  of  the  cylinder.  Fill  the  measuring 
cylinder  with  aggregate.  Raise  the  funnel  to  the  upper  rack. 
Weigh  the  water  which  must  be  added :  1.  to  reach  the  top  level 
of  the  aggregate  if  the  material  settles ;  2.  to  fill  the  cylinder. 

Calculate  the  per  cent  of  voids  as  in  method  1. 

For  any  aggregate  which  settles,  obtain  also  the  ratio  of  the 
volume  of  water,  added  to  reach  the  top  level  of  the  aggregate, 
to  the  actual  volume  of  the  settled  aggregate. 

Method  2  is  slightly  more  accurate  than  method  1,  since  less 
air  is  entrained  when  small  particles  make  up  the  aggregate.  The 
per  cent  of  moisture  greatly  influences  the  per  cent  of  voids  in 
sands.  For  sand  and  in  general,  method  3  will  give  more  reliable 
results. 

Method  3.  Specific  Gravity  Method.  Determine  the  specific 
gravity  of  each  of  the  materials  in  the  following  manner :  Weigh 
the  glass  graduate  first  empty,  then  half  filled  with  water.  Check 
the  increase  in  weight  with  the  volume.  Weigh  out  about  the 
same  volume  of  dry  aggregate,  add  and  agitate  if  necessary  to 
remove  any  air  bubbles.  Quickly  note  the  exact  rise  of  the  water 
level  before  the  material  absorbs  any  appreciable  amount  of 
water. 

The  specific  gravity  of  the  material  equals  the  weight  of 
aggregate  added,  divided  by  the  weight  of  displaced  water. 

Weigh  the  wooden  measuring  box.  Fill  even  full  with  aggre- 
gate; shake  to  cause  settlement  and  weigh  again.  Calculate  the 
per  cent  of  voids  by  using  the  specific  gravity  above  obtained. 
If  the  material  is  not  dry,  its  weight  must  be  corrected  for  the 
per  cent  of  moisture  present.  Determine  the  per  cent  of  moisture 
by  weighing  out  about  50  grams,  then  thoroughly  drying  in  the 
oven  and  reweighing. 

Mix  thoroughly  an  amount  of  dry  sand  and  broken  stone  in 
the  proportions  1 :2,  by  volume  shaken,  sufficient  to  slightly 
more  than  fill  the  wooden  measuring  box.  Fill  the  box  even  full 

[12] 


with  this  mixture,  shake  slightly  to  cause  settlement,  and  obtain 
its  net  weight.     Calculate  the  per  cent  of  voids  in  the  mixture. 

Tabulate  the  results  of  the  several  determinations. 

References.  Determination  of  Voids.  1.  Concrete — Plain  and  Ee- 
inforced,  by  Taylor  and  Thompson,  pages  160-168.  2.  A  Treatise  on 
Masonry  Construction,  by  Baker,  pages  143-146,  101-102,  91-94.  3.  Bul- 
letin 23,  University  of  Illinois  Engineering  Experiment  Station,  by  I.  O. 
Baker. 


[13] 


TEST    No.   4 

TENSILE   STRENGTH   OF   NEAT   CEMENT  AND 
STANDARD  CEMENT  MORTAR 

Apparatus.  Balance  with  scoop  and  counterweight,  one  set 
of  weights,  Vicat  needle  apparatus,  thirty  standard  briquette 
moulds,  five  six-mould  gang  clamps,  six  surface  plates,  one  100  cc. 
graduate,  thermometer,  two  small  trowels,  two  scraping  knives, 
two  pans,  one  water  pitcher. 

Operations.  Determination  of  Normal  Consistency.  Since 
the  strength  of  neat  cement  and  cement  mortars  at  early  periods 
varies  greatly  with  the  amount  of  water  used  in  mixing,  to  obtain 
comparable  results  for  various  cements,  it  is  necessary  to  make 
the  mixture  of  a  standard  consistency.  The  method  for  deter- 
mining this  consistency  is  given  in  the  "Standard  Methods  of 
Testing  Cement,"  pages  13-15. 

Determine  the  normal  consistency  for  the  cement  sample 
assigned,  using  500  grams  for  each  trial  batch.  Add  the  whole 
of  the  trial  per  cent  of  water  at  once ;  use  a  new  batch  of  cement 
for  each  trial.  "Penetration  of  the  needle"  is  construed  to 
mean  its  position  of  final  rest  after  one  or  two  minutes,  there 
being  no  vibration  of  the  apparatus.  After  the  normal  consist- 
ency for  the  cement  paste  is  determined,  the  per  cent  of  water 
for  standard  sand  mortars  is  determined  empirically  from  the 
table  on  page  15. 

Moulding  of  Briquettes.  Following  the  directions  on  pages 
17-21,  "Standard  Methods  for  Testing  Cement,"  each  student 
will  mould  independently  nine  neat  and  six  mortar  briquettes. 
For  the  neat  briquettes  mix  two  batches  of  800  grams  each ;  for 
the  mortar  mix  one  batch  of  300  grams  of  cement  with  900  grams 
of  standard  sand. 

Each  student  should  carefully  put  a  small  identifying  mark 
near  the  end  of  each  of  his  briquettes ;  do  not  change  nor  injure 
the  middle  section  of  a  briquette  by  the  marking.  Place  the 

[14] 


finished  briquettes  in  the  moist  closet,  together  with  a  card  indi- 
cating the  party  number. 

The  temperature  of  the  room  should  be  as  near  70°  F.  as  pos- 
sible, since  lower  temperatures  retard  the  setting  of  cement  and 
hence  decrease  its  strength  at  early  periods. 

The  laboratory  data  for  each  batch  mixed  should  be  presented 
in  tabular  form  and  contain  the  following  items :  Batch  number, 
brand  of  cement,  temperatures  of  room  and  water,  weights  and 
percentages  of  various  ingredients,  number  of  briquettes  moulded, 
date  made,  identification  marks. 

Testing  of  Briquettes.  In  order  to  fulfill  the  conditions  of 
the  standard  methods  of  testing  cement  it  will  be  necessary  for 
students  to  come  to  the  laboratory  to  make  the  first  tensile  test 
as  nearly  twenty-four  hours  after  the  moulding  of  the  briquettes 
as  possible.  The  tests  at  seven  and  twenty-eight  days  can  be 
made  at  the  regular  laboratory  periods  in  addition  to  the  assign- 
ment for  those  days.  Failure  to  test  at  the  proper  time  will 
make  it  necessary  to  repeat  the  whole  test.  The  report  should 
be  submitted  after  making  the  twenty-eight  day  test. 

Fairbank's  automatic  cement  testing  machine  will  be  used. 

Before  testing  the  briquettes,  check  the  rate  of  application 
of  the  load  as  follows :  Support  the  poise  arm  and  allow  the  shot 
to  run  into  the  bucket  for  sixty  seconds.  Transfer  the  bucket 
with  shot  to  the  opposite  end  of  the  arm,  put  counterweight  in 
its  place  and  weigh  out.  If  the  machine  does  not  record  600  Ibs. 
adjust  the  valve  regulating  the  flow  of  shot  and  repeat  until  the 
load  is  applied  at  the  rate  of  600  Ibs.  per  minute. 

Briquettes  should  be  tested  as  soon  as  they  are  removed  from 
the  water.  Before  testing,  dry  each  briquette  with  a  cloth  and 
weigh. 

With  the  shot  bucket  empty  and  the  poise  set  at  zero  bring 
the  clips  of  the  machine  together  with  the  fast  motion  and  insert 
the  briquette.  See  that  the  briquette  is  accurately  centered  and 
bears  uniformly  against  the  clips  at  the  surfaces  of  contact. 
Tighten  with  the  fast  motion  until  the  poise  arm  is  balanced: 

[15] 


then  transfer  to  the  slow  motion.  Eelease  the  shot  and  keep  the 
poise  arm  balanced  by  turning  the  slow  motion  wheel  until  the 
briquette  breaks.  Note  the  time  of  shot  flow.  Weigh  out  as  above. 

Each  student  will  test  three  neat  cement  briquettes  at  ages  of 
twenty-four  hours,  seven  days  and  twenty-eight  days,  and  three 
mortar  briquettes  at  ages  of  seven  days  and  twenty-eight  days. 

Submit  the  test  results  in  a  tabular  form  including  the 
following  items:  Number  of  briquette,  batch  number,  mixture, 
weight,  age,  tensile  strength,  remarks. 

References.  Tensile  Strength  of  Cement.  1.  A  Treatise  on  Masonry 
Construction,  by  Baker,  pages  71-84,  121-124.  2.  The  Elasticity  and 
Kesistance  of  the  Materials  of  Engineering,  by  Burr,  pages  352-378. 
3.  Practical  Cement  Testing,  by  W.  P.  Taylor,  pages  101-156.  4.  Portland 
Cement,  by  Meade,  pages  316-350.  5.  Cements,  Limes  and  Plasters,  by 
Eckel.  6.  Concrete — Plain  and  Eeinforced,  by  Taylor  and  Thompson. 


[16] 


TEST    No.   5 

MOULDING   CUBES  FOR  COMPRESSION   TESTS   OF 
CEMENT   MORTAR 

Apparatus.  Balance  with  scoop  and  counterweight,  one  set 
of  metric  weights,  sixteen  two-inch  cast  iron  cube  moulds,  two 
250  c.c.  graduates,  two  mixing  pans,  two  slate  slabs,  two  trowels, 
two  scraping  knives,  two  small  pans,  one  water  pitcher,  Vicat 
needle  apparatus. 

Operations.  Determine  as  in  test  4  the  amount  of  water 
required  for  a  cement  paste  of  normal  consistency.  All  mixtures 
are  to  be  of  normal  consistency,  which  for  mortars  is  obtained 
empirically  from  the  following  table : 

PERCENTAGES  OF  WATER  FOR  STANDARD  MIXTURES 


Neat 

1:1 

1:2 

1:3 

1:4 

1:5 

1:6 

18 

12.0 

10.0 

9.0 

8.4 

8.0 

7.6 

19 

12.3 

10.2 

9.2 

8.5 

8.1 

7.7 

20 

12.7 

10.4 

9.3 

8.7 

8.2 

7.8 

21 

13.0 

10.7 

9.5 

8.8 

8.3 

7.9 

22 

13.3 

10.9 

9.7 

8.9 

8.4 

8.0 

23 

13.7 

11.1 

9.8 

9.1 

8.5 

8.1 

24 

14.0 

11.3 

10.0 

9.2 

8.6 

8.2 

If  the  sand  is  damp  the  per  cent  of  moisture  should  be  deter- 
mined as  in  test  3,  so  that  proper  allowance  can  be  made  for  it. 

Using  the  sands  and  cement  provided,  each  student  will  mix 
independently  four  batches  of  mortar.  For  each  batch  use  600 
grams  of  dry  material.  Mould  two  cubes  from  each  batch  and 
carefully  weigh  the  mortar  left  over.  Student  1  will  make  mix- 
tures: neat,  1:1,  1:2,  1:3,  using  ordinary  sand;  student  2  will 
make  mixtures  1 :4,  1 :5,  1 :6,  using  ordinary  sand,  and  1 :3,  using 
standard  sand.  All  proportions  are  to  be  determined  by  weigh- 
ing. 

First  thoroughly  mix  the  sand  and  cement  dry.     With  the 

[17] 


thumb  or  trowel,  but  without  ramming,  carefully  press  the 
mortar  into  the  corners  and  completely  fill  the  moulds.  Smooth 
the  top  off  evenly.  Place  an  identifying  mark  on  each  cube  and 
leave  a  card  with  the  party  number  on  each  slate  slab. 

Using  the  RDecific  gravity  for  cement  and  sand  as  determined 
in  tests  2  and  3  calculate  the  density  of  the  mortar  of  each  batch. 

For  each  batch  mixed  tabulate  the  following  data :  Batch 
number,  brand  of  cement,  kind  of  sand,  weights  and  proportions 
of  various  ingredients,  density  of  mortar,  size  of  cubes,  number 
of  cubes,  marks  on  cubes,  date  made. 

References.  Density  of  Mortar.  1.  Concrete — Plain  and  Keinforced, 
by  Taylor  and  Thompson,  pages  134-140.  2.  A  Treatise  on  Masonry 
Construction,  by  Baker,  pages  108-110. 


[18] 


TEST    No.   6 

MOULDING  SPECIMENS  FOR   COMPRESSION   TEST   OP 

CONCRETE 

Apparatus.  Two  6-in.  cylinder  moulds  12  in.  long  with  bot- 
tom plates,  one  8-in.  cylinder  mould  16  in.  long,  one  6  x  6  x  6  in. 
cube  mould,  one  set  of  measuring  boxes  of  capacities  i/o  cu.  ft., 
14  cu.  ft.,  and  %  cu.  ft.,  one  mixing  pan,  two  shovels,  two  trowels, 
two  tamping  rods,  one  water  pail.  Note: — The  sectional  areas 
of  the  6-in.  and  8-in.  cylinders  are  respectively  30  sq.  in.  and 
50  sq.  in. 

Operations.  Mix  two  batches  of  concrete  of  proportions 
1 :2  :4  by  volume  shaken.  Use  for  each  batch  %  cu.  ft.  of  rock, 
14  cu.  ft.  of  sand  and  %  cu.  ft.  of  cement.  See  that  the  boxes 
are  even  full  after  shaking.  Weigh  each  measure  of  materials 
used  and  calculate  its  average-  weight  per  cubic  foot.  Allow  for 
any  moisture  present. 

First  spread  the  broken  stone  in  an  even  layer  in  the  mixing 
pan;  place  the  sand  next  and  the  cement  on  top.  Thoroughly 
mix  the  cement,  sand  and  rock  dry.  Add  water  gradually  and 
mix  until  the  mass  is  uniformly  incorporated  and  of  a  rather 
wet  plastic  consistency.  Weigh  the  amount  of  water  used  for 
each  batch. 

In  filling  the  moulds  put  some  of  the  richer  portions  of  the 
mix  at  the  bottom  so  as  to  form  an  even  bearing  surface.  Add 
the  concrete  gradually  and  tamp  continually  to  force  out  air 
bubbles  and  to  obtain  a  uniformly  dense  specimen.  Heap  the 
material  slightly  on  top  and  when  the  water  has  settled  smooth 
the  surface  off  evenly  and  level  with  the  mould. 

Stamp  the  party  number  on  each  specimen.  Weigh  the  con- 
crete left  over. 

Calculate  the  average  density  of  the  concrete  made. 

The  data  for  each  batch  should  contain  the  following  items 

[19] 


in  tabular  form:  Batch  number,  kinds  of  material,  weights  of 
materials  per  cubic  foot,  amounts  and  proportions  of  materials 
by  volume  and  weight,  number  of  specimens  made,  dimensions 
of  specimens,  date  made. 

References.  Density  of  Concrete.  1.  A  Treatise  on  Masonry  Construc- 
tion, by  Baker,  pages  137-139.  2.  The  Laws  of  Proportioning  Concrete: 
Transactions  American  Society  of  Civil  Engineers,  vol.  59,  page  67. 


[20] 


TEST    No.   7 

MOULDING  SPECIMENS  FOR  TENSION  TEST   OF 
CONCRETE 

Apparatus.  Three  6-in.  cylinder  moulds  27  in.  long  with 
end  plates  and  bolts,  one  set  of  measuring  boxes  of  capacities 
y2  cu.  ft.,  i/4  cu-  ft.,  and  %  cu  ft.,  one  mixing  pan,  two  shovels, 
two  trowels,  two  tamping  rods,  one  water  pail. 

Operations.  Mix  two  batches  of  concrete  of  rather  wet  con- 
sistency according  to  the  directions  of  paragraphs  1  and  2  under 
Operations  in  test  6. 

Arrange  the  bolts  in  the  lower  plate  so  that  their  heads  extend 
alternately  about  three  inches  and  five  inches  into  the  mould. 
Clamp  the  shell  squarely  about  the  lower  plate.  Fill  the  mould 
to  about  one  inch  above  the  bolt  heads  with  a  1 :1  mortar  tem- 
pered to  a  soft  plastic  consistency.  Tamp  the  mortar  about  the 
bolts,  being  careful  not  to  disturb  the  position  of  the  bottom 
plate.  Add  the  concrete  gradually  up  to  a  point  five  inches 
below  the  top  of  the  mould,  tamping  continually.  Adjust  the 
top  plate  squarely  in  place  with  the  bolt  heads  extending  into 
the  mould.  Through  the  opening  in  the  top  plate  fill  in  1:1 
mortar  of  a  semi-fluid  consistency,  so  that  it  will  completely  fill 
the  mould.  After  settlement  of  the  material  remove  any  excess 
above  the  lower  surface  of  the  top  plate.  Leave  a  card  with  the 
party  number  on  each  specimen. 

The  ends  are  made  of  a  richer  mixture  to  make  them  stronger 
than  the  body  of  the  specimen. 

The  data  for  each  batch  should  be  tabulated  and  contain : 
Batch  number,  kinds  of  material,  weights  of  materials  per  cubic 
foot,  amounts  and  proportions  of  materials  by  volume  and 
weight,  number  of  specimens  made,  dimensions  of  specimens, 
date  made. 


[21] 


References. 


[22] 


TEST    No.   8 

MOULDING  SPECIMENS  FOR  TEST  OF  BOND  BETWEEN 
STEEL  AND  CONCRETE 

Apparatus.  Six  moulds  4x6x6  in.,  two  threaded  specimens 
each  of  plain  round,  twisted  square  and  corrugated  steel  rein- 
forcement bars,  one  set  of  measuring  boxes  of  capacities  y2  cu.  ft., 
14  cu.  ft.,  and  %  cu.  ft.,  one  mixing  pan,  two  shovels,  two  trowels, 
two  tamping  rods,  one  water  pail. 

Operations.  Mix  a  batch  of  concrete  of  a  rather  wet  con- 
sistency according  to  the  directions  of  paragraphs  1  and  2  under 
Operations  in  test  6. 

Carefully  adjust  the  steel  rods  in  the  moulds.  Add  the  con- 
crete slowly  and  tamp  continually,  but  be  careful  not  to  displace 
the  rods,  as  their  axes  must  be  perpendicular  to  the  front  faces 
of  the  specimens.  Fill  the  moulds  completely.  After  the  material 
has  settled  smooth  the  top  off  evenly  and  stamp  the  party  number 
on  each  specimen. 

The  data  for  each  batch  should  be  tabulated  and  contain: 
Batch  number,  kinds  of  materials,  weights  of  materials  per  cubic 
foot,  amounts  and  proportions  of  materials  by  volume  and  weight, 
number  of  specimens  made,  dimensions  of  specimens,  sizes  of 
rods,  imbedded  length  of  rods,  areas  of  bond  surface  of  rods, 
date  made. 

References. 


[23] 


TEST    No.   9 

MOULDING  REINFORCED   CONCRETE   BEAMS   FOR 
FLEXURE  TEST  OF  CONCRETE 

Apparatus.  Two  beam  moulds  4  x  6  x  72  in.,  two  plain  round 
reinforcement  bars,  two  deformed  reinforcement  bars,  one  set 
of  measuring  boxes  of  capacities  y2  cu  ft.,  14  cu.  ft.,  and  %  cu.  ft., 
two  mixing  pans,  two  shovels,  two  trowels,  two  water  pails,  two 
tamping  rods. 

Operations.  Mix  four  batches  of  concrete  of  rather  wet  con- 
sistency according  to  the  directions  of  paragraphs  1  and  2  under 
Operations  in  test  6. 

First  tamp  into  the  mould  a  layer  of  concrete  one  inch  thick; 
then  insert  the  bars  through  the  holes  in  the  ends  of  the  mould. 
See  that  the  bars  are  straight  when  in  position.  Fill  the  mould 
gradually,  tamping  continually.  After  the  concrete  has  settled, 
smooth  the  top  off  even  with  the  mould.  Stamp  the  party  number 
at  each  end  of  the  beam. 

Two  beams  will  be  moulded.  Use  the  plain  bars  in  one  and 
the  deformed  bars  in  the  other. 

The  data  for  each  batch  should  be  tabulated  and  contain: 
Batch  number,  kinds  of  material,  weights  of  materials  per  cubic 
foot,  amounts  and  proportions  of  materials  by  volume  and  weight, 
number  of  specimens  made,  dimensions  of  specimens,  sizes  and 
sectional  areas  of  rods,  per  cent  of  reinforcement,  date  made. 

References. 


[24] 


TEST    No.   10 

COMPRESSION  TEST  OF  CEMENT  MORTAR  CUBES 

Apparatus.  Testing  machine  equipped  for  compression,  with 
spherical  seated  base-plate,  one  balance,  one  set  of  metric  weights, 
pan  for  broken  cubes. 

Materials.    Mortar  cubes  previously  made  by  the  party. 

Operations.  Dry  each  cube  with  a  cloth  and  weigh  just  before 
testing.  Apply  the  pressure  on  the  moulded  faces ;  if  these  are 
uneven  bed  them  with  blotting  paper. 

Read  the  directions  for  operation  of  testing  machines  on 
page  5. 

After  accurately  centering  the  specimen  in  the  machine  lower 
the  movable  head  until  it  just  clears  the  cube.  Adjust  base-plate 
so  that  the  bearing  surface  of  the  cube  is  parallel  to  the  upper 
plate;  this  insures  a  uniform  pressure  over  the  entire  cross- 
section  when  the  load  is  applied. 

Use  the  slowest  speed  of  the  machine  to  apply  the  load.  Keep 
the  poise  arm  floating  throughout  the  test.  Record  the  maximum 
load.  Note  the  character  of  the  failures. 

Each  student  will  test  his  own  cubes  independently,  alternat- 
ing in  the  use  of  the  machine  with  other  students  assigned  to  the 
same  test. 

Report.  Submit  results  in  tabular  form,  giving  the  following 
facts  for  each  cube:  Batch  number,  kinds  and  proportions  of 
materials,  age,  dimensions,  total  weight,  weight  in  pounds  per 
cubic  foot,  density,  total  crushing  load,  crushing  strength  in 
pounds  per  square  inch. 

Using  the  average  results  of  both  members  of  the  party  con- 
struct a  diagram  on  coordinate  paper  using  crushing  strengths 
as  ordinates  and  percentages  of  cement  by  weight  as  abscissae. 

References.     1.    Principles   of   Keinforced   Concrete    Construction,    by 

[25] 


Turneaure  and  Maurer,  pages  12-13.     2.  Concrete — Plain  and  Keinforced, 
by  Taylor  and  Thompson,  page  136.     3.  Tests  of  Metals. 


[26] 


TEST    No.  11 

COMPRESSION  TEST  OF  CONCRETE 

Apparatus.  Testing  machine  equipped  for  compression,  with 
spherical  seated  base-plate,  scales,  plaster  of  Paris,  water  pitcher, 
trowel,  mixing  pan,  circular  cast  iron  capping  plates. 

Materials.  Concrete  compression  specimens  previously  made 
by  the  party,  except  one  small  cylinder. 

Operations.  Weigh  each  specimen.  Bed  the  end  surfaces 
with  a  thin  layer  of  plaster  of  paris.  Cap  these  with  the  iron 
plates  when  the  plaster  is  still  soft.  Press  the  plates  firmly 
against  the  plaster  and  be  careful  to  place  them  perpendicular 
to  the  axis  of  the  specimen. 

Read  the  directions  for  operation  of  testing  machines  on 
page  5. 

Center  the  specimen,  with  its  ends  thus  prepared,  in  the 
testing  machine.  Adjust  the  base-plate  for  parallelism  of  top 
bearing  surface  and  upper  plate  of  the  machine.  Use  the 
slowest  speed  for  applying  the  load.  Keep  the  poise  arm  floating 
throughout  the  test.  Record  the  load  when  the  first  crack  appears 
and  the  maximum  load.  Sketch  the  failures. 

Report.  Give  the  following  results  for  each  specimen :  Batch 
number,  shape  and  dimensions,  kinds  and  proportions  of 
materials,  age,  total  weight,  weight  per  cubic  foot,  density,  total 
loads  at  first  crack  and  maximum,  strengths  at  first  crack  and 
maximum  in  pounds  per  square  inch. 

References.  1.  A  Treatise  on  Masonry  Construction,  by  Baker,  pages 
194-208.  2.  Principles  of  Eeinforced  Concrete  Construction,  by  Turneaure 
and  Maurer,  pages  11-15.  3.  Tests  of  Metals. 


[27] 


TEST    No.  12 

TENSION  TEST  OF  CONCRETE 

Apparatus.  Testing  machine  equipped  for  tension,  with 
spherical  seated  tension  head,  flanged  grips,  nuts  and  spacing 
rods  for  concrete  tension  tests,  small  wrench. 

Materials.  Concrete  tension  cylinders  previously  made  by 
the  party. 

Operations.  Bolt  a  grip  on  the  bottom  of  each  cylinder ;  then 
bolt  the  top  grip  against  the  three  spacing  rods  placed  in  their 
proper  position  between  the  grips.  Screw  the  nuts  uniformly, 
but  not  too  tightly.  This  method  of  attaching  the  grips  insures 
that  the  applied  tension  is  axial. 

Read  the  directions  for  operation  of  testing  machines  on 
page  5. 

Insert  the  specimen  in  the  machine.  Apply  the  load  by  the 
slowest  speed  and  keep  the  poise  arm  floating  throughout  the 
test.  Record  the  maximum  load ;  sketch  the  failure. 

Report.  Tabulate  the  following  quantities  for  each  specimen : 
Batch  number,  dimensions,  kinds  and  proportions  of  materials, 
age,  total  load,  strength  in  pounds  per  square  inch. 

References.  1.  A  Treatise  on  Masonry  Construction,  by  Baker,  page 
202.  2.  Principles  of  Eeinforced  Concrete  Construction,  by  Turneaure 
and  Maurer,  pages  15-17. 


[28] 


TEST  No.  13 

TEST  OF  BOND  BETWEEN  CONCRETE  AND  STEEL 

Apparatus.  Testing  machine  equipped  for  bond  test,  with 
spherical  seated  tension  head. 

Materials.  Specimens  for  bond  tests  previously  made  by  the 
party. 

Operations.  Read  the  directions  for  operation  of  testing 
machines  on  page  5. 

Pass  the  rod  of  the  test  specimen  through  the  opening  in  the 
movable  head  of  the  testing  machine  and  screw  the  tension  grip 
on  to  it.  Adjust  the  specimen  so  that  the  concrete  bearing  surface 
is  parallel  to  the  lower  surface  of  movable  head.  If  the  concrete 
surface  is  uneven  it  should  be  bedded  with  plaster  of  Paris  and 
capped  with  a  special  perforated  plate. 

Apply  the  load  with  the  slowest  speed  and  keep  the  poise  arm 
floating  throughout  the  test.  Record  the  maximum  load  and  the 
frictional  resistance  after  the  maximum  is  reached. 

Report.  Give  the  following  results  for  each  specimen :  Batch 
number,  dimensions,  kinds  and  proportions  of  materials,  age, 
kind  and  size  of  bar,  bond  area,  maximum  load,  frictional  resist- 
ance, maximum  and  frictional  bond  strength  in  pounds  per  square 
inch  of  bond  area. 

Give  the  ratio  of  average  bond  strengths  of  deformed  and 
plain  bars. 

References.  1.  Principles  of  Eeinforced  Concrete  Construction,  by 
Turneaure  and  Maurer,  pages  33-40.  2.  Bulletin  no.  8,  Engineering  Ex- 
periment Station,  University  of  Illinois.  3.  Bulletin  no.  321,  University 
of  Wisconsin. 


[29] 


TEST    No.  14 

REINFORCED  CONCRETE   BEAM  TEST 

Apparatus.  Testing  machine  equipped  for  flexure  test,  with 
box  channel  beam,  beam  supports,  third  point  loading  apparatus, 
deflection  measuring  apparatus,  scale,  small  square. 

Materials.  Two  reinforced  concrete  beams  previously  made 
by  the  same  party. 

Operations.  Weigh  the  beam  and  measure  its  dimensions. 
Support  the  beam  on  a  60-in.  span,  with  its  middle  under  the 
center  of  the  movable  head.  Draw  vertical  lines  on  both  sides 
of  the  beam  at  the  supports,  center  and  third  points.  Apply  the 
load  at  the  third  points ;  if  the  top  of  the  beam  is  uneven  at  these 
points,  bed  the  plates  of  the  loading  apparatus  in  plaster  of  Paris. 

Read  the  directions  for  operation  of  testing  machines  on 
page  5. 

Attach  the  deflection  measuring  apparatus  and  obtain  its  zero 
for  reading  for  an  initial  load  of  100  Ibs.  Record  the  deflection 
for  each  100-lb.  load  increment  up  to  a  total  load  of  1000  Ibs. ;  for 
each  200-lb.  increment  thereafter.  Note  the  deflection  and  load 
when  the  first  crack  appears,  also  the  position  of  the  crack.  Keep 
the  poise  arm  floating  throughout  the  test.  Record  the  maximum 
load.  Make  a  scale  sketch  of  the  failure  on  cross-section  paper. 

Demolish  the  beam  and  return  the  reinforcement  bars  to  their 
proper  place. 

Report.  For  each  test  construct  a  diagram  on  coordinate 
paper  with  loads  in  pounds  as  ordinates  and  deflections  in  inches 
as  abscissae.  Join  the  plotted  points  with  a  smooth,  not  a  sinuous 
curve.  Mark  as  the  elastic  limit  that  point  on  the  curve  where 
the  deflection  ceases  to  be  proportional  to  the  load.  Submit  curve 
in  pencil  to  the  instructor  for  approval  before  inking. 

Give  the  following  quantities  for  each  beam :  Batch  number, 
kinds  and  proportions  of  materials,  kind,  disposition  and  per  cent 

[30] 


of  reinforcement,  age,  dimensions,  total  weight,  weight  in  pounds 
per  cubic  foot,  manner  of  loading,  loads  at  first  crack,  elastic 
limit  and  maximum. 

Calculate  the  following  quantities  for  each  beam:  Case  1 — • 
Neglect  tension  in  concrete  and  assume  that  compression  in  con- 
crete varies  lineally.  Position  of  neutral  surface.  Fiber  stresses 
in  concrete  and  steel,  bond  developed  between  concrete  and  steel 
and  maximum  shear  in  concrete  at  the  elastic  limit  and  maximum 
load.  Case  2 — Neglect  tension  in  concrete  and  assume  that 
compression  in  concrete  varies  parabolically.  The  same  quantities 
as  in  case  1.  In  both  cases  assume  the  ratio  of  the  coefficients  of 
elasticity  of  steel  and  concrete  as  15. 

Eeferences.  1.  Principles  of  Eeinforced  Concrete  Construction,  by 
Turneaure  and  Maurer,  pages  56-72;  108-112.  2.  A  Treatise  on  Masonry 
Construction,  by  Baker,  pages  224-236. 


[31] 


TEST  No.  15 

SIEVE  ANALYSIS  OF  CONCRETE  AGGREGATES 

Purpose.  To  obtain  the  granulometric  composition  of  the 
component  parts  of  a  concrete  aggregate. 

Apparatus.  Sand  shaker;  balance  with  scoop  and  counter- 
weights ;  the  following  sizes  of  sand  sieves :  Nos.  4,  10,  20,  30,  40, 
50,  80,  100  and  200 ;  also  perforated  rock  screens  of  the  following 
diameters :  |  in.,  f  in.,  £  in.,  f  in.,  J  in.,  J  in.,  1  in.,  1J  in..  1J  in., 
2  in.,  and  2J  in. ;  measuring  box. 

Materials.  Group  1.  A  fine  sand,  a  coarse  sand,  several 
assortments  of  crusher  run  of  broken  stone  ranging  in  size  from 
J  in.  to  If  in.  Group  2.  A  fine  sand,  a  coarse  sand,  several  assort- 
ments of  screened  river  gravel  ranging  in  size  from  J  in.  to  1^  in. 

Operations. 

Sieve  Analysis  of  Sand 

Make  a  sieve  analysis  of  each  of  the  sands  of  group  1  or  2, 
as  directed,  in  the  following  manner. 

From  a  representative  portion  of  bin  material  select,  by  a 
quartering  process,  a  sample  of  approximately  1500  gm.  Dry 
this  thoroughly  in  the  oven ;  then  determine  its  weight  in  pounds 
per  cubic  foot. 

Arrange  the  sand  sieves  in  order  with  the  largest  size  on  top 
and  the  pan  at  the  bottom.  Place  the  nest  of  sieves  in  the  shaker. 

Place  1000  gm.  of  the  dried  sample  in  the  top  sieve,  cover  the 
sieve,  clamp  the  nest  in  the  shaker  and  shake  for  1000  complete 
oscillations  at  a  uniform  rate  of  333  per  minute.  Weigh  the 
residue  on  each  sieve  and  in  the  pan. 

Sieve  Analysis  of  Gravel  or  Crushed  Rock 

Make  a  sieve  analysis  of  each  of  the  gravels  or  broken  stones 
of  group  1  or  2,  as  directed,  in  the  following  manner : 

From  a  representative  portion  of  bin  material,  select,  by  a 
quartering  process,  a  sample  of  about  3500  gm.  Dry  this 
thoroughly  in  the  oven ;  then  determine  its  weight  in  pounds 
per  cubic  foot. 

[32] 


Weigh  out  accurately  a  portion  as  close  to  3000  gm.  as  prac- 
ticable. Shake  this  by  hand  successively  through  all  the  rock 
screens,  starting  with  the  largest  size.  Shake  on  each  sieve  until 
complete  rejection  occurs.  Weigh  the  amount  which  passes  each 
screen,  and,  as  a  check,  the  amount  rejected. 

Report.  The  separation  size  of  a  sieve  is  the  distance  in  the 
clear  between  its  meshes.  The  effective  separation  size  of  a  sieve 
is  defined  as  that  separation  size  which  is  computed  to  be 
numerically  equal  to  the  diameter  of  a  sphere  whose  volume  is 
equal  to  the  average  of  the  volumes  of  angular  sand  or  rock 
particles  which  just  pass  the  sieve.  The  effective  size  of  a  sieve, 
therefore,  must  be  determined  experimentally  and  it  varies 
slightly  according  to  the  general  form  of  the  sand  or  rock  par- 
ticles analyzed. 

The  following  table  gives  the  effective  separation  sizes  of  the 
above  sieves. 

Effective  Separation  Sizes  Effective  Separation  Sizes 

of  Sand  Sieves  of  Rock  Screens 


Size  Effective  size 

Sieve  No.  in  inches  Screen  size  in  inches 

4          0.231  iin.  0.213 

10          0.077  I  0.34 

20          0.050  \  0.45 

30          0.024  f  0.56 

40          0.018  1  0.68 

50          0.014  | 

80          0.0061          1  0.87 
100          0.0059          \\ 

200          0.0036          1J  1.34 

2  1.68 

2|  1.98 

Describe  each  material  and  give  its  weight  in  pounds  per 
cubic  foot.  Submit  the  results  of  each  sieve  analysis  in  tabular 
form,  giving  actual  separation  size  of  sieve  or  screen,  its  effective 
size,  weight  passing,  percentage  passing.  Indicate  checks  in 
weighing. 

References. 

1.  Concrete,  Plain  and  Eeinforced,  by  Taylor  and  Thompson  (1909 

edition),  pp.  193-200. 

2.  The  Modern  Asphalt  Pavement,  by  Richardson   (1912  edition), 

pp.  59-72. 

[33] 


TEST  No.  16 

GRANULOMETRIC  PROPORTIONING  OF  CONCRETE 
AGGREGATES 

Purpose.  To  determine  the  relative  amounts  of  separately 
screened  materials  of  various  sizes  ranging  from  fine  sand  to  a 
given  maximum  size  of  rock,  required  to  produce  a  concrete  of 
the  greatest  density  possible  with  the  given  materials. 

Materials.    The  same  as  those  used  in  Test  No.  15. 

Operations.  Plot  the  sieve  analysis  curves  of  all  the  materials 
analyzed  in  Test  No.  15  on  a  sheet  of  tracing  cross-section  paper 
11x36  in.  Plot  "percentage  passing"  as  ordinates  and  " effec- 
tive sizes"  as  abscissas.  Using  the  data  at  the  bottom  of  page  203, 
Concrete,  Plain  and  Reinforced,  by  Taylor  and  Thompson  (1909 
edition),  draw  in  pencil  on  the  cross-section  paper  the  ideal 
curve  for  a  practical  mix. 

Following  the  methods  outlined  in  Appendix  IV  of  Taylor 
and  Thompson,  determine  the  relative  amounts  of  the  several 
materials,  so  that  the  sieve  analysis  curve  of  their  combination 
approaches,  throughout  its  entire  length,  the  ideal  curve  as  nearly 
as  is  practicably  possible.  Draw  in  pencil  the  curves  of  several 
trial  combinations.  Submit  for  approval  by  instructor  before 
inking  the  trial  curve  which  is  finally  selected  as  the  best.  Com- 
pute the  proportions  of  the  several  materials  for  a  1  :  and  for 
a  1  :9  concrete,  where  the  components  of  the  aggregate  are  meas- 
ured by  volume  separately. 

Report.  Explain  in  detail  the  method  of  solution.  Include 
all  computations.  Ink  and  label  all  curves  in  black.  In  the 
lower  right  corner  of  the  diagram  place  a  title  giving  a  statement 
of  the  problem,  the  kinds,  sizes  and  proportions  by  volume,  of 
materials. 

References. 

1.  Concrete,  Plain  and  Beinforced,  by  Taylor  and  Thompson  (1909 

edition),  pp.  200-210. 

2.  '-The  Laws  of  Proportioning  Concrete,"  by  W.  B.  Fuller  and 

S.  E.  Thompson,   Transactions  of  the  American  Society  of 
Civil  Engineers,  vol.  59,  p.  67. 

[34] 


c/ 


TEST  No.  6A 

DENSITY  OF  CONCRETE 

Purpose.  To  determine  the  density  of  concrete  to  be  used  for 
compression  specimens. 

Materials.  \  cubic  foot  dry  crushed  rock,  ^  cubic  foot  of  dry 
sand,  |  cubic  foot  of  cement. 

Apparatus.  8  x  16-in.  cylindrical  measuring  mould  with 
piston,  one  set  of  measuring  boxes  of  capacities  ^  cubic  foot, 
J  cubic  foot,  and  -J  cubic  foot,  one  mixing  pan,  one  shovel,  one 
trowel,  one  tamping  rod,  one  water  pail. 

Operations.  Before  mixing  any  concrete,  weigh  dry,  the 
mixing  pan,  the  shovel,  the  trowel  and  the  tamping  rod.  Use 
no  other  tools  than  these  for  mixing.  Weigh  out  J  cubic  foot 
of  dry  crushed  rock,  j  cubic  foot  of  dry  sand,  and  ^  cubic  foot 
of  cement.  Jar  the  materials  in  the  measuring  boxes  and  scrape 
off  the  top  level  with  the  top  of  the  box  before  weighing. 

Spread  the  broken  stone  in  an  even  layer  in  the  mixing  pan ; 
place  the  sand  next  and  the  cement  on  top.  Thoroughly  mix  the 
cement,  sand  and  rock  dry.  Add  water  gradually  and  mix  until 
the  mass  is  uniformly  incorporated  and  of  a  quaking  consist- 
ency. Weigh  the  amount  of  water  used.  The  mixture  should 
not  be  too  wet.  Take  great  care  not  to  lose  any  of  the  ingred- 
ients either  during  mixing  or  while  filling  into  the  measuring 
cylinder. 

Measure  accurately  the  mean  diameter  and  height  of  the 
measuring  cylinder.  Weigh  it  including  the  piston.  Place  the 
bottom  of  the  cylinder  on  a  truly  level  surface  and  fill  it  with 
concrete  in  about  2-inch  layers,  tamping  each  layer  before  adding 
the  next.  Occasionally  while  filling  the  cylinder  stir  the  concrete 
remaining  in  the  mixing  pan  to  keep  it  uniformly  incorporated. 
Fill  the  cylinder  to  about  one  inch  of  the  top.  See  that  the  top 

[35] 


surface  of  the  concrete  is  truly  level.  The  tamping  should  not 
be  so  vigorous  as  to  force  an  excess  of  water  to  the  surface. 
Insert  the  piston  and  allow  it  to  rest  without  added  pressure 
on  the  concrete.  Measure  from  top  of  cylinder  to  top  of  piston 
at  the  120  degree  points  of  the  cross-section  of  the  cylinder. 
To  obtain  the  depth  of  the  concrete  add  the  circumferential  thick- 
ness of  the  piston  to  the  mean  of  these  three  measurements. 
Weigh  the  cylinder  with  concrete  and  piston.  Calculate  the 
volume  of  the  concrete. 

Weigh  the  mixing  box  with  remaining  concrete,  together  with 
uncleaned  shovel,  trowel  and  tamping  rod.  Check  the  difference 
in  weight  between  the  measuring  cylinder  empty  and  filled  with 
concrete  with  the  difference  in  weights  of  materials  used  and 
remaining. 

Calculate  the  density  of  the  concrete,  assuming  that  the  ratio 
of  ingredients  in  the  concrete  remaining  is  the  same  as  the  ratio 
of  their  original  weights.  For  the  specific  gravities  of  the  sand 
and  crushed  rock  use  the  values  posted  on  the  bulletin  board. 
Consult  reference  No.  1  under  Test  No.  6  for  the  method  of 
making  the  computation  of  density. 

All  other  conditions  being  the  same,  the  density  of  concrete 
having  a  given  percentage  of  cement  indicates  how  effectively 
the  voids  in  a  set  concrete  have  been  reduced  by  granulometric 
proportioning  of  the  aggregate.  The  denser  a  concrete,  the 
stronger  it  is.  For  given  materials,  density  determinations  are 
useful  to  give  an  immediate  clue  as  to  the  best  concrete  the 
materials  can  produce  without  waiting  for  such  concrete  to  age 
for  compression  tests,  but  compression  tests  alone  can  determine 
what  the  actual  strength  of  such  a  concrete  is.  For  given 
materials  small  variations  in  density  produce  large  variations 
in  strength.  An  increase  of  1  per  cent  in  the  density  constant 
may  produce  an  increase  of  20  per  cent  in  the  compressive 
strength  of  a  Ic :  2s :  4r  concrete  in  the  form  of  cubes  at  the  age 
of  three  months.  It  therefore  follows  that  great  care  must  be 
exercised  in  making  density  determinations,  particularly  in 
regard  to  weights  of  ingredients,  in  regard  to  moisture  (all 

[36] 


ingredients  must  be  dry  before  mixing)  and  in  regard  to  account- 
ing for  all  ingredients  originally  weighed.  The  density  should 
be  obtained  to  the  nearest  tenth  of  a  per  cent. 

Describe  all  the  ingredient  materials.     Report  all  quantities 
and  calculations  in  tabular  form. 

References. 

1.  A   Treatise   on   Masonry   Construction,   by   Baker,   pp.    137-139 

(1909  edition). 

2.  The   Laws   of   Proportioning   Concrete:    Transactions    American 

Society  of  Civil  Engineers,  vol.  59,  p.  67  on. 


[37] 


TEST  No.  3 

SPECIFIC  GRAVITY  OF  SAND  AND  CRUSHED  ROCK 
VOIDS  IN  CONCRETE  AGGREGATES 

Purposes.  To  determine  the  specific  gravity  of  sand,  of 
crushed  rock.  To  determine  the  percentage  of  voids  in  sand,  in 
crushed  rock  and  in  a  mixture  of  sand  and  crushed  rock. 

Apparatus.  One  1000  cc.  glass  graduate,  one  500  cc.  glass 
graduate,  one  balance  with  scoop  and  counterweight,  table  and 
overhanging  arm,  one  set  of  metric  weights,  one  wooden  measur- 
ing box  of  J  cubic  foot  capacity,  one  water  pail,  one  galvanized 
iron  measuring  cylinder  with  bottom  inlet,  weighing  scales 
sensitive  to  one-quarter  of  an  ounce,  scale  graduated  to  tenths 
of  an  inch,  some  thread,  battery  jar,  a  large  square  pan. 

Materials.  Two  cubic  feet  of  crushed  concrete  rock,  one  cubic 
foot  of  concrete  sand,  both  thoroughly  dry. 

Operations.    Make  the  following  determinations : 

1.  Specific  gravity  of  sand. 

2.  Specific  gravity  of  crushed  rock. 

3.  Percentage  of  voids  in  sand  by  two  methods. 

4.  Percentage  of  voids  in  crushed  rock  by  two  methods. 

5.  Percentage  of  voids  in  a  mixture  of  sand  and  crushed 

rock  by  two  methods. 

1.  Specific  Gravity  of  Sand. 

Weigh  in  grams  the  lOOOcc.  graduate  first  empty,  then  about 
half  filled  with  water.  Check  increase  in  weight  with  volume  of 
water.  Weigh  about  500  grams  of  dry  sand.  Note  exact  weight. 
Pour  the  weighed  sand  into  the  graduate ;  agitate  to  remove  air 
bubbles.  Quickly  note  exact  rise  in  water  level  before  the  sand, 
if  other  than  siliceous,  can  absorb  any  appreciable  amount  of 
water. 

The  specific  gravity  of  the  sand  equals  its  weight  in  air 
divided  by  the  weight  of  displaced  water. 

[38] 


2.  Specific  Gravity  of  Crushed  Rock. 

Make  trial  weighings  first  in  air,  then  in  water,  of  a  dry  rock 
particle  which  is  approximately  cubical  and  weighs  in  air  between 
29  and  31  gm.  This  is  to  determine  approximately  the  loss  in 
weight  on  immersion.  The  determination  is  approximate  because 
of  absorption  by  the  stone  during  weighing. 

Carefully  weigh  in  air  another  dry  rock  particle  of  similar 
size  and  shape  and  from  the  previous  weighings  calculate  the 
approximate  weight  of  the  second  particle  when  immersed  in 
water.  Set  the  scale  at  this  calculated  weight.  With  the  thread 
suspend  the  rock  from  the  scale  pan  so  as  to  completely  immerse 
it  and  quickly  determine  its  exact  weight  when  immersed. 

The  apparent  specific  gravity  of  the  rock  is  given  by  the 

W 

expression   -== ==-,  where  W  equals  the  weight  in  grams  of 

\  \  \V  -» 

the  dry  rock  particle  in  air  and  Wt  equals  its  weight  in  grams 
just  after  immersion. 

3.  Percentage  of  Voids  in  Sand  by  Two  Methods. 

Method  1.  By  Direct  Measurement  with  Water. — Weigh  in 
grams  the  1000  cc.  graduate  first  empty,  then  about  half  filled 
with  water.  Note  the  height  of  water  surface.  Check  increase 
in  weight  with  volume  of  water.  Measure  out  500  cc.  of  dry  sand 
in  the  smaller  graduate.  Jar  graduate  gently  to  settle  sand. 
Pour  sand  into  large  graduate.  Agitate  to  remove  air  bubbles. 
Quickly  note  new  height  of  water  surface. 

The  difference  between  500  cc.  and  the  displaced  volume  of 
water  in  the  graduate  equals  the  voids  in  cubic  centimeters  in 
500  cc.  of  sand.  Calculate  the  percentage  of  voids.  Note  the 
volume  of  the  settled  sand  in  the  large  graduate.  Account  for 
the  change  in  volume. 

Method  2.  Indirectly  ~by  Measurement  of  the  Solid  Contents 
of  the  Sand. — Weigh  in  grams  the  1000  cc.  graduate  first  empty, 
then  filled  with  dry  sand.  Jar  very  gently  to  settle  the  sand. 
The  volume  of  solid  sand  particles  in  the  graduate  equals  the 
increase  in  weight  divided  by  the  specific  gravity  of  the  sand. 
The  volume  of  voids  in  cubic  centimeters  in  1000  cc.  of  sand 

[39] 


equals  1000  cc.  minus  the  volume  of  solid  sand  particles.  Calcu- 
late the  percentage  of  voids  in  the  sand.  Compare  with  the 
result  of  Method  1.  Give  reasons  for  difference. 

4.  Percentage  of  Voids  in  Crushed  Rock  by  Two  Methods. 

Method  1.  An  Approximate  Field  Method. — Determine  the 
volume  of  the  water  pail  by  weighing  it  first  empty,  then  com- 
pletely filled  with  water.  Its  volume  in  cubic  feet  equals  the 
difference  in  weight  in  pounds  divided  by  62.24. 

Soak  in  water  for  thirty  minutes  enough  crushed  rock  to  fill 
the  pail.  Then  remove  the  rock  from  the  water  and  set  it  aside 
in  the  large  square  pan  to  drain.  When  its  surfaces  have  become 
free  of  surplus  water  place  it  in  the  pail,  shake  it  to  cause  settle- 
ment and  level  it  even  with  the  top  of  the  pail.  Weigh  the 
amount  of  water  which  can  be  added  to  fill  the  pail  completely. 
Calculate  its  volume  by  dividing  this  weight  in  pounds  by  62.24. 
This  equals  the  volume  of  voids  in  a  volume  of  crushed  rock 
equal  to  that  of  the  water  pail.  Calculate  the  percentage  of 
voids  in  the  crushed  rock. 

Method  2.  By  Direct  Measurement  with  Water. — In  this 
method  the  water  is  introduced  into  the  container  from  below  so 
as  to  reduce  the  inclusion  of  air  to  a  minimum. 

Determine  the  volume  of  the  galvanized  iron  cylinder  by 
measuring  its  mean  diameter  and  height.  Place  the  funnel 
attached  to  the  rubber  tube  which  leads  to  the  bottom  of  the 
cylinder  in  the  lower  rack  which  is  level  with  the  bottom  of 
the  cylinder.  Fill  the  tube  and  funnel  with  water  to  the  level 
of  the  bottom  of  the  cylinder.  Then  weigh  the  cylinder  to  the 
nearest  quarter  of  an  ounce. 

Fill  the  cylinder  with  dry  crushed  rock.  Shake  to  cause 
settlement.  Level  the  rock  even  with  the  rim  of  the  cylinder. 
Weigh  the  cylinder  filled  with  rock.  Place  the  funnel  in  the 
upper  rack.  Pour  water  into  the  cylinder  through  the  funnel, 
measuring  with  a  graduate  the  amount  required  to  fill  it  com- 
pletely. Note  the  length  of  time  required.  Weigh  the  cylinder 
when  it  is  completely  filled  with  water.  Check  increase  in  weight 
with  measured  volume  of  water  added. 

[40] 


Since  the  rock  absorbs  water,  a  correction  must  be  made  for 
the  percentage  of  absorption  of  the  rock  for  the  time  required 
to  fill  the  cylinder.  Determine  the  percentage  of  absorption  of 
the  rock  as  follows: 

Percentage  of  Absorption  of  Rock 

Determine  exact  weights  in  air  and  on  immersion  of  a  dried 
rock  particle  which  is  approximately  cubical  in  shape  and  weighs 
in  air  between  29  and  31  gm.  To  do  this,  follow  in  detail  the 
directions  given  in  the  first  two  paragraphs  in  subdivision  2 
above,  entitled, '  *  Specific  Gravity  of  Crushed  Rock. ' '  After  deter- 
mining the  exact  weight  on  immersion  allow  the  particle  to 
remain  immersed  for  the  time  required  to  fill  the  cylinder  when 
making  the  determination  of  voids  and  then  again  weigh  the 
particle  while  it  is  still  immersed. 

The  water  absorbed  in  pounds  per  cubic  foot  of  solid  rock  is 

^y  yf 

given  by  the  expression,  — ==r — =±-    X  62.24,  where  W  equals 

rr    W ^ 

the  weight  in  grams  of  the  dried  sample  in  air ;  W^  the  weight 
in  grams  of  the  sample  in  water  just  after  immersion  and  W2, 
the  final  weight  in  grams  of  the  sample  while  it  is  still  immersed. 
The  weight  of  distilled  water  in  pounds  per  cubic  foot  at  tem- 
perature of  77°  Fahr.  is  62.24  Ibs.  The  percentage  of  absorption 

•yy     ^7- 

by  weight  is  given  by  the  expression   -  -^-== —  1  X  100. 

Calculate  the  percentage  of  voids  in  the  crushed  rock,  making 
the  correction  for  absorption. 

5.  Percentage  of  Voids  in  a  Mixture  of  Sand  and  Crushed  Rock 
by  Two  Methods. 

Method  1.  By  Direct  Measurement  with  Water. — In  the 
wooden  measuring  box  measure  off  and  weigh  ^  cubic  foot  of 
dry  crushed  rock  which  has  been  slightly  shaken  to  cause  settle- 
ment. Place  the  rock  in  the  pan.  Measure  off  similarly  an 
amount  of  dry  sand  equal  in  volume  to  ^  cubic  foot  multiplied 
by  the  percentage  of  voids  in  the  crushed  rock  as  determined 
by  Method  2  of  subdivision  4  above,  entitled,  "  Percentage  of 
Voids  in  Crushed  Rock  by  Two  Methods." 

[41] 


Weigh  this  amount  of  sand.  Add  the  sand  to  the  crushed 
rock  in  the  pan  and  mix  these  thoroughly.  Determine  the  per- 
centage of  voids  in  the  mixture  by  Method  2  of  subdivision  4 
above,  entitled,  "Percentage  of  Voids  in  Crushed  Rock  by  Two 
Methods." 

To  do  this,  weigh  the  amount  of  thoroughly  settled  mixture 
required  to  fill  the  cylinder.  Measure  by  volume  and  check  by 
weight  the  amount  of  water  required  to  fill  the  cylinder.  Calcu- 
late the  percentage  of  voids  in  the  mixture,  making  the  correc- 
tion for  absorption.  In  computing  this  correction  for  absorption, 
assume  that  the  ratio  of  sand  to  rock  by  weight  in  the  cylinder  is 
the  same  as  the  ratio  of  their  weights  before  mixing.  The  correc- 
tion for  absorption  need  not  be  made  for  sand  when  it  is  siliceous. 

Assuming  the  percentage  of  voids  in  the  sand  as  given  by  the 
average  of  the  two  methods  in  subdivision  3  above,  entitled,  ' '  Per- 
centage of  Voids  in  Sand. by  Two  Methods,"  compute  the  per- 
centage of  voids  in  the  above  mixture  of  sand  and  crushed  rock, 
assuming  that  the  sand  completely  fills  the  voids  in  the  crushed 
rock  as  they  existed  before  addition  of  the  sand.  Compare  this 
computed  quantity  with  the  measured  percentage  of  voids. 
Draw  conclusions. 

Method  2.  Indirectly  ~by  Measurement  of  the  Solid  Contents 
of  the  Mixture. — Make  a  mixture  of  dry  crushed  rock  and  dry 
sand  of  the  same  proportions  and  amounts  as  for  Method  1  above. 
Weigh  the  amount  of  this  mixture  required  to  fill  the  \  cubic 
foot  measuring  box.  Before  levelling  top  surface  of  mixture 
even  with  the  rim  of  the  box,  jar  slightly  to  cause  settlement. 
Assume  the  ratio  of  sand  to  crushed  rock  by  weight  in  the  box 
to  be  the  same  as  the  ratio  of  their  weights  before  mixing. 

The  volume  in  cubic  centimeters  of  either  solid  sand  or  solid 
rock  particles  in  the  box  equals  its  weight  in  grams  divided  by 
its  specific  gravity.  This  volume  in  cubic  feet  equals  the  weight 
in  pounds  divided  by  the  quantity,  (specific  gravity  multiplied 
by  62.24).  Compute  separately  the  volumes  of  solid  sand  and 
of  solid  rock  particles  in  the  box.  Compute  the  percentage  of 
voids  in  the  mixture. 

Compare  Methods  1  and  2  of  subdivision  5. 

[42] 


Tabulate  the  results  of  all  determinations. 

When  only  two  materials  are  available  for  concrete,  a  sand 
and  a  coarse  aggregate,  gravel  or  crushed  rock,  void  determina- 
tions are  useful  to  give  a  first  approximate  proportion  for  a 
mixture  of  the  sand  and  rock  which  will  produce  a  concrete 
with  minimum  voids.  The  exact  proportions  of  sand  and  rock 
are  then  determined  as  follows :  Using  the  above  proportion  as  a 
basis,  various  concrete  mixtures  are  made  in  which  these  pro- 
portions are  varied  slightly  either  way,  the  percentage  of  cement 
by  weight  in  terms  of  the  total  dry  aggregate  in  each  case  being 
the  same  and  the  amount  of  mixing  water  used  in  each  case  being 
such  as  to  produce  the  same  consistency  in  all  cases.  The  density 
of  each  of  these  concrete  mixes  is  then  determined.  That  mixture 
is  selected  as  best  whose  density  is  greatest. 

When  there  is  a  variety  of  available  sands  of  different  sizes 
and  a  variety  of  available  coarse  aggregates  of  different  sizes 
the  most  direct  method  of  proportioning  so  as  to  produce  the 
densest  concrete  is  outlined  in  Test  No.  16. 


[43] 


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